Vacuum brake assist

Is there a vacuum brake assist that just bolts on to an 89 xj 40 withe no additional plates or addapters?

Not that I’m aware of. But the common retrofit with adapter plate is not
very difficult and works well. IMHO

Cheers, Alan

I read one person used an 8 inch double diaphragm unit and made his own adapter plate, I dpnt even know where or what to look for? Jaguar parts or will any unit work?

I bought a simple kit here
It uses a booster from '80-'87 XJ6

One caveat; it requires removal of the self leveling rear suspension (if you still have it)

Should be some more info in the archives.


David …

I did the vacuum conversion years ago on my '89 XJ40 and and have been very happy with it. Not something you install with just a screwdriver, but not really that difficult either. Alan is right on with all his info.

  1. You can do this only if you’ve converter you self leveling rear shocks to a conventions system.

  2. The vacuum booster you want to use is from a series II or III XJ6. I tried an 8" double diaphragm
    aftermarket booster and it DIDN’T WORK ! (not enough boost). A lot of wasted effort.

  3. You can buy an adapter plate but it’s not that hard to fabricate one yourself or have it made. You’ll
    need to cut down a couple of the brake pedal tower bolts so the adapter will fit. You also need to
    drill and tap the intake manifold to accept a brass fitting for the vacuum line.

  4. No need to disconnect the master brake cylinder but I believe I had to slightly enlarge the holes to
    bolt it to the booster.

  5. The cooling system header tank will have to be moved slightly forward to make room for the master
    cylinder on a left hand drive car.

  6. You’ll have to try and keep from hitting your head when you jump for joy after seeing how much “no longer needed” stuff you’ll now be able to remove from your car.

Certainly not a complete list but this gives you some idea of what’s involve. Total cost including a remanufactured booster and adapter plate under $200. In all honesty the braking effort at the pedal is just a tad higher then I would like (maybe 10% less effort would be perfect) but I don’t even notice it anymore. Small trade off for getting rid of the habitually leaking “green monster” system !

Can I get a new one from an auto parts store?

Groove, is always there with good info.
The “kit” includes reference to a vacuum check or residual valve. Specifies one easily available at your local FLAPS.

You can get a rebuilt booster from Oregon Power Brake. “Booster Dewey” knows exactly what is needed, and is at least a little familiar with the swap.

Nfi, etc